1. Field of the Invention
The present invention relates to a "ready" indicator for high-voltage switchgear and more specifically to a "ready" indicator for use with an automatic control device found in high-voltage switchgear which indicates the capability of both the control device and the switchgear to perform their intended functions and to give an indication of such capability to persons not familiar with the internal workings of either the control device or the switchgear.
2. Brief Discussion of the Prior Art
Numerous control systems and detectors for polyphase electrical systems and for equipment containing such systems are well-known. One type of equipment often used or found in polyphase electrical systems is metal-enclosed switchgear which usually contains a series combination for each phase of the system of an interrupter switch and a power fuse. An interrupter switch is an electrical switch which may be manually or automatically operated (opened or closed) as dictated by the requirements of the system or by requirements of loads connected thereto. An interrupter switch has the capability of opening the phase in which it is contained and upon such opening interrupting load currents and currents of lesser magnitude flowing in the phase. Such interruption normally includes the extinguishment or suppression of a high-voltage arc which forms when opening of the phase is attempted. The arc is extinguished or suppressed in a controlled environment so as to cause little if any distress to the switch itself, to the metal-enclosed switchgear in which the switch is contained, or to the electrical system to which this switchgear is connected.
The power fuses serially connected to each interrupter switch are essentially protective devices. Specifically, these power fuses respond to fault currents or other overcurrents flowing in the phase in which they are connected and interrupt such fault currents or other overcurrents upon the occurrence thereof. Interruption effected by the power fuses involves the extinguishment or suppression of the high-voltage arc which is formed incident thereto in a controlled environment so as to cause little if any distress to the electrical system or to other equipment connected thereto.
Often, it is critical or important that certain loads energized by the electrical system not be without electrical power for more than abbreviated times. In this event, two independent electrical sources are often provided, each source containing appropriate switchgear connected thereto. Under normal conditions, one of the sources, often termed a preferred source, is connected to the loads through the interrupter switches in the switchgear connected thereto. The other electrical source is utilized only if the preferred source is unable to supply proper electrical power. The other electrical source is therefore often referred to as an alternate source. Connection of the alternate source to the load therefore involves the opening of the interrupter switches in the switchgear connected to the preferred source and the closing of the interrupter switches in the alternate source.
Any persons, including utility employees, who are responsible for the maintenance, repair, or operation of switchgear, often do not have detailed knowledge concerning the internal working of the switchgear. For example, the switchgear connected to the preferred electrical source and to the alternate electrical source may be of the type in which the interrupter switches in the switchgear connected to the preferred source are normally closed and the switches in the switchgear connected to the alternate source are normally open. The switches may be operated by automatic operators, the operator associated with the normally closed interrupter switches being capable only of automatically opening such switches, and the operator associated with the normally open switches being capable of only closing such switches. Should this be the case, return of both sets of switches to their initial condition requires manual operation. Moreover, either electrical source may be selected to be the preferred source, while the other may be selected to be the alternate source. Because of this, the switchgear may permit the removal of each switch operator and appropriate disassociation thereof from its switches and interchanging the switch operators in the switchgear. Further the switch operators may involve stored energy sources such as springs which may be in a charged or uncharged condition.
Thus, at any given time it may be important for an operator or other person to quickly ascertain the condition, open or closed, or the switches, whether or not the respective switch operators are appropriately coupled to the switches, whether or not the correct switch operator is associated with the correct switch (depending upon which source is the preferred source and which is the alternate source) and whether or not the stored energy source in each switch operator is appropriately charged or capable of operating the operator to open or close the switches associated therewith in the appropriate manner.
There are many other conditions of the switchgear which it is desirable that a human operator be able to quickly ascertain. As noted above, such operators often do not have detailed knowledge of the internal workings of the switchgear. It goes without saying that they also do not have the detailed knowledge of the switch operators.
Accordingly, an object of the present invention is the provision of a "ready" indicator for high-voltage switchgear which is convenient and inexpensive and reliable, and from which a human operator may easily ascertain whether or not the condition of the switchgear is appropriate in view of the requirements and conditions of electrical sources associated with the switchgear and of loads connected thereto.